【 Weak current College 】 intelligent parking fieldbus CAN-bus network

Abstract: the life of convenience, making intelligent parking everywhere. This article describes how to use the fieldbus connection modernization CAN-bus smart parking each discrete Terminal, as well as the use of fieldbus CAN-bus networking after competitive advantage; and from a technical perspective, elaborated in the next few years the development trend of the intelligent car park.

1 foreword as society is changing lifestyle, science and technology of continue to progress, people require more user-friendly, intelligent living conditions. No hands-on, as much as possible to let the smart system instead of a manual way, for the effective management and implementation. The current traffic situation ever more complex, such as road and parking difficult issues reduced the city's work and life, efficiency obliges us to find an easy solution to the problem. Intelligent car park is in this background came into being. Intelligent parking generation not only standardized the urban traffic management and vehicle management, expanded the city's capacity, in security also has significant security, yet convenient and other intelligent systems interfaces (such as intelligent buildings, intelligent community, etc.) to form a more perfect logistics and equipment management system. 2 present situation at present smart parking communication intelligent of the parking lot, management also lack the ordering of commonality among the facilities are poor, leading system integrators and users of equipment selection varieties less, realization of insufficiency, system characteristics not sharp, etc. Press the smart car communication analysis, part of the early manufacturers use a serial RS-485 or RS-232 bus as a means of communication between the device; at the same time, some of the advanced manufacturers have adopted CAN-bus bus or an Ethernet network EtherNet as a means of communication.

By the way communications RS-232 parking system has great limitation, can only implement point-to-point operation, the burden on the central processor, not easy system expansion, communication distance is very short, not suitable for remote operations; and system costs are relatively high. Using RS-485 bus systems in the overall performance is better than RS-232 system, because it is easy to expand in the form of the bus, but as the parking system intelligence level increasingly demanding, features strong, bus nodes increasingly, RS-485 bus efficiency low, system of real-time performance difference, communication reliability, low maintenance cost is high, the late network project debugging complex, transmission distance is not ideal, single bus can hook application node, and so is not flexible enough and defect gradually manifested; intelligent parking system extensions are also affected by the restrictive RS-485 itself, and cannot accommodate large and medium-sized smart car park control needs. State-of-the-art communication systems of CAN-bus bus is intelligent parking of mainstream development direction. Use this kind of industrial-grade communication mode, you can ensure the reliability of data communications, real-time; and, the actual construction cost, CAN-bus bus and RS-485 way cost approximately equivalent, even in relatively large parking system, the overall cost of CAN bus also slightly lower than RS-485 system. Due to the can bus fault-tolerant performance is good, you can greatly reduce the latter part of the maintenance, repair and expansion costs. However, most of the smart car adopts CAN-bus bus and RS-232, RS-485 communications mix, to a certain extent may cause network load imbalance limits CAN-bus bus play maximum performance advantages. The following will be formed by CAN-bus bus parking fees and management system, for example, describes a set of intelligent car park improvement programmes, thereby reflecting the overall advantages CAN-bus bus. 3 intelligent parking CAN-bus programme 3.1 CAN-bus introduction CAN (Controller Area Network) bus was made by Germany BOSCH company, mainly used for automotive internal measurement and control of the data communication between the centers. Because of its good performance in the world is widely used in other areas, such as industrial automation, automotive, building construction, Elevator network, electricity distribution and security fire and many other fields, and gradually become the main means of communication.

Fieldbus CAN-bus characteristics: 1, the international standard industrial field bus, transport, reliable, real-time high; 2, transmission distance (farthest 10KM), transfer rates (up to 1Mbps); 3, single bus maximum 110 nodes and can easily expand the number of nodes; 4, bus on each node of the status of equality, non-slave, unexpected data can be transmitted in real time; 5, non-destructive bus arbitration techniques that many nodes in parallel to the bus data bus utilization high; 6, error CAN node automatically shut down and cut off and bus links, and does not affect bus communication; 7, the message is short frame structure and a hardware CRC, interference data probability is small, extremely low error rate; 8, was not successfully sent messages are automatically sent, hardware features, transmission reliability is very high; 9, a hardware address filtering features that simplify software development agreements; 10, communication media available ordinary twisted pair and coaxial or optical etc; 11, CAN-bus bus system structure is simple, the cost performance is extremely high. Introduction to communication programme in General 3.2 covered car park of almost all control features, including export and import control, remote control, yard orientation, yard parking auto detection, intelligent lighting control the shaft. Programme does not include the transmission of audio, video, audio, video of the transmission is generally separate from the control bus. The entire system, communication backbone of only one twisted pair, various communication terminal controller directly connected to the bus; and, various controllers in the network status can be equal, so there is no "host" and "the concept of" from the machine, any node can start data transfer, to avoid the use of host polling mode RS-485, thus protecting the numberIt is in real-time. In CAN-bus bus, either as point-point communication or multicast mode of communication, real-time performance and flexibility can be good. For example, you can according to car parking space probes inside the car of a direct transfer into and out of the change, the number of parking spaces to monitor displayed; without having to transfer to the management machine, which will manage machine to parking monitor. Course management machine also can receive the information for the database records.

Intelligent Car Park communication distance from CAN-bus bus baud rate restriction; 20Kbps communication speed, you can achieve communication distance 3KM (use the same twisted pair) that meets most needs. In this scenario, follow the location of the parking system is divided into two parts: the vehicles of import and export controls, internal control shaft. Export and import control vehicle 3.3 vehicles and export control section of the main function is to access management, charges, tickets and shows, etc. System cabling structure as shown in Figure 1. System with linear CAN-bus network topology, device nodes connected by extension CAN-bus mainline. In the yard entrance, local sense detects vehicles pass, entry controller to send a signal to the computer management node, start the whole request management system (prior to this system is in hibernation to save energy), the system immediately into work mode. Entrance to the controller through the radio frequency or GPRS mode read vehicle electronic card information, and through CAN-bus bus transfer to the management computer and the camera's vehicle information (cars, car, etc.) in contrast, if this is the "legal" user opens gates, light green traffic lights to allow vehicles to pass. When the Barrier Gate Office to sense detection vehicles have passed, and the entrance to sense does not detect the new vehicles will still be imported controller to the computer management node report system idle, you can enter a sleep mode. Other features, such as export controls, features, etc, all charges can be managed in the same way. System, the management node used to install Universal PC-CAN interface card, the PC and perform different functions, install a different location of terminal equipment. Commonly used PC-CAN interface card: PCI-CAN interface card, ISA-CAN interface card, USBCAN interface card, PC104-CAN interface card, EtherNet-CAN interface cards or parallel port CAN interface cards may be based on the system of communication requirements for a reasonable choice. 3.4 yard yard internal control within the control of some of the major feature is the space vehicle guidance, testing, and lighting control. As shown in Figure 2, figure in the yard is divided into four parking areas: A, B, c and D zones. 4 districts locational boot system housed in the yard entrance indicating regional orientation and the current remaining empty digits. The location of the boot system consists of a controller with a CAN-bus bus interface. When a vehicle or vehicle owners and a related area, the area of lighting is lit, the departure of the vehicle or vehicle owners, lights automatically turns off and is not related to the current access zone lighting will not be lit so that you can maximize the energy conservation, to extend equipment life, this is a large parking lot in effect will be more prominent. In access, car parking number changes, the system can be timely detected the changes and to the main controller and location guide signs report to refresh the current record and display. Such a system, using CAN-bus bus communication, the network is very simple, reliable, as shown in Figure 2. Each parking area there is a separate zone controller, with CAN-bus interface for management of lighting and parking area. As shown in the figure, the red line is a line, through the zone controller for direct control of the light will light off. The green line is a single bus, and communication, and detector(UD) CAN-bus bus, forming a convenient secondary data communication network. Of course, detector(UD) network set up you can also use CAN-bus manner, basically not be affected by the restriction of the number of parking spaces, and you can easily implement device management, fault location and many other specific functions. 4 system advantages of these two parts are connected, you can form a complete intelligent parking system. The entire system, not only can you achieve unattended, and other CAN-bus system connections, such as wuyeguanlizhongxin, community centers, convenience of operation and management of the overall system. Use CAN-bus bus, as well as custom communication protocols, design software offers very significant advantages, so that the system's overall performance is improved. At the same time, using CAN-bus bus can greatly reduce the entire Smart car park in the device extension, system upgrades, terminal maintenance costs of the inputs. Also, the more large-scale intelligent parking system, the advantages of using CAN-bus bus will be more obvious – features a good, low cost, management and maintenance cost savings. Practice has proved that adopts CAN-bus bus in smart car running can obtain good social and economic interests. CAN-bus bus has been successfully operating in the country more intelligent parking, yard equipment, vehicle management, vehicle toll stations, etc. This is the domestic multitudinous traffic control network for reliable, automated, unattended operation, direction of development.